Material Testing - Jorhat Engineering College

LABORATORY MANUAL

Material Testing

(ME 305)

Department of Mechanical Engineering

Jorhat Engineering College

Jorhat – 785007 (Assam)

(ii)

COLLEGE VISION AND MISSION

Vision:

To develop human resources for sustainable industrial and societal growth

through excellence in technical education and research.

Mission:

1. To impart quality technical education at UG, PG and PhD levels through good

academic support facilities.

2. To provide an environment conducive to innovation and creativity, group work and

entrepreneurial leadership.

3. To develop a system for effective interactions among industries, academia, alumni

and other stakeholders.

4. To provide a platform for need-based research with special focus on regional

development.

DEPARTMENT VISION AND MISSION

Vision:

To emerge as a centre of excellence in mechanical engineering and maintain it

through continuous effective teaching-learning process and need-based research.

Mission:

M1: To adopt effective teaching-learning processes to build students capacity and

enhance their skills.

M2: To nurture the students to adapt to the changing needs in academic and industrial

aspirations.

M3: To develop professionals to meet industrial and societal challenges.

M4: To motivate students for entrepreneurial ventures for nation-building.

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Program Outcomes (POs)

Engineering graduates will be able to:

1. Engineering knowledge: Apply the knowledge of mathematics, science, engineering

fundamentals, and an engineering specialization to the solution of complex

engineering problems.

2. Problem analysis: Identify, formulate, review research literature, and analyze

complex engineering problems reaching substantiated conclusions using first

principles of mathematics, natural sciences, and engineering sciences.

3. Design/development of solutions: Design solutions for complex engineering

problems and design system components or processes that meet the specified needs

with appropriate consideration for the public health and safety, and the cultural,

societal, and environmental considerations.

4. Conduct investigations of complex problems: Use research-based knowledge and

research methods including design of experiments, analysis and interpretation of data,

and synthesis of the information to provide valid conclusions.

5. Modern tool usage: Create, select, and apply appropriate techniques, resources, and

modern engineering and IT tools including prediction and modelling to complex

engineering activities with an understanding of the limitations.

6. The engineer and society: Apply reasoning informed by the contextual knowledge to

assess societal, health, safety, legal and cultural issues and the consequent

responsibilities relevant to the professional engineering practice.

7. Environment and sustainability: Understand the impact of the professional

engineering solutions in societal and environmental contexts, and demonstrate the

knowledge of, and need for sustainable development.

8. Ethics: Apply ethical principles and commit to professional ethics and responsibilities

and norms of the engineering practice.

9. Individual and team work: Function effectively as an individual, and as a member

or leader in diverse teams, and in multidisciplinary settings.

10. Communication: Communicate effectively on complex engineering activities with

the engineering community and with society at large, such as, being able to

comprehend and write effective reports and design documentation, make effective

presentations, and give and receive clear instructions.

11. Project management and finance: Demonstrate knowledge and understanding of the

engineering and management principles and apply these to one’s own work, as a

member and leader in a team, to manage projects and in multidisciplinary

environments.

12. Life-long learning: Recognize the need for, and have the preparation and ability to

engage in independent and life-long learning in the broadest context of technological

change.

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Programme Educational Objectives (PEOs)

The Programme Educational Objectives of Department of Mechanical Engineering are given

below:

PEO1: Gain basic domain knowledge, expertise and self-confidence for employment,

advanced studies, R&D, entrepreneurial ventures activities, and facing

challenges in professional life.

PEO2: Develop, improve and maintain effective domain based systems, tools and

techniques that socioeconomically feasible and acceptable and transfer those

technologies/developments for improving quality of life.

PEO3: Demonstrate professionalism through effective communication skill, ethical

and societal commitment, team spirit, leadership quality and get involved in

life-long learning to realize career and organisational goal and participate in

nation building.

Program Specific Outcomes (PSOs)

The programme specific outcomes of Department of Mechanical Engineering are given

below:

PSO1: Capable to establish a career in Mechanical and interdisciplinary areas with

the commitment to the society and the nation.

PSO2: Graduates will be armed with engineering principles, analysing tools and techniques

and creative ideas to analyse, interpret and improve mechanical engineering systems.

Course Outcomes (COs)

At the end of the course, the student will be able to:

CO1 Determine the hardness of materials by Brinell and Rockwell hardness testing machines.

CO2 Determine the toughness of materials by Charpy Pendulum Impact Testing machine.

CO3 Determine the compressive strength of materials by Compression testing machine

CO4 Determine the torsional strength of materials by pendulum Torsion Testing machine.

CO5 Determine the tensile strength of materials by Universal testing machine.

Mapping of COs with POs:

COs PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12 PSO1 PSO2

CO1 2 2 2 1 1 1 1 1 2

CO2 2 2 2 1 1 1 1 1 2

CO3 2 2 2 1 1 1 1 1 2

CO4 2 2 2 1 1 1 1 1 2

CO5 2 2 2 1 1 1 1 1 2

(v)

STUDENT PROFILE

NAME :

ROLL NUMBER :

SECTION :

SEMESTER : 3rd Semester

YEAR :

PERFORMANCE RECORD

EXP.

NO. TITLE OF EXPERIMENT

REMARKS /

GRADE

1 Rockwell Hardness Test.

2 Brinell Hardness Test.

3 Charpy Pendulum Impact Test.

4 Compressive Stress Test.

5 Torsion Test.

6 Tension Test.

OFFICE USE

Checked By :

Overall Grade / Marks :

Signature of Teacher :

(1)

Jorhat Engineering College Material Testing Lab

Experiment No. 1

TITLE: Rockwell Hardness Test.

OBJECTIVE:

To determine hardness of a flat mild steel and high carbon steel specimen.

THEORY:

The hardness of a material is its resistance to

penetration under a localized pressure or resistance

to abrasion. Hardness test provides an accurate,

rapid and economical way of determining the

resistance of the material to deformation.

In Rockwell hardness test, the instrument

measures the depth of penetration made by a

particular indenter under a definite amount of load

and indicates it as a dimensionless hardness

number on a Dial Indicator.

Initial a Preliminary Test Force (Minor Load) is applied to the test piece and the

Indenter penetrates through a certain depth into the test piece. Since the surface of the

test piece may not be fully free from irregularities, hence this initial penetration

eliminates any effect of surface finish on the test results and sets the Zero Reference

Line for the test procedure.

Figure 1.1: Indentation under different test loads

(2)


Next, an Additional Test Force (Major Load) is applied and the Indenter

penetrates through the maximum depth possible. This load is kept in application for a

definite amount of time (dwell time) and then released to allow elastic recovery in the

test piece. There will remain some residual depth of penetration (Permanent Depth of

Penetration) on the test piece and this residual depth is converted into a dimensionless

Hardness Number as indicated on the Dial Indicator.

A variety of penetrators and standard loads can be used; giving a series of

different scales identified by capital letters A, B, C, D, E, F, G, H, K, N and T. Refer

Table 1.1 for all the details.

The Rockwell method is much faster than any other methods of hardness testing

and produces an indentation of the order of 0.005 inch. It is therefore suitable for thin

specimen.

PRECAUTIONS:

The thickness of the test piece should be at least ten times the permanent indentation

depth for cone indenters and fifteen times the permanent indentation depth for ball

indenters.

The test should be carried out at ambient temperature within the limits of 10℃ to

35℃ . However, because temperature variations may affect the results, hence for

better results, the test can be carried under controlled environment.

The test surface should be smooth and even, free from oxide scale, foreign matters

and, in particular, completely free from lubricants. Exceptions include reactive metals,

like titanium, which might adhere to the indenter. In such situations, a suitable

lubricant such as kerosene may be used. The use of a lubricant shall be reported on

the test report.

PROCEDURE:

1. Place the Test Piece on the Test Piece Bed.

2. Press the Handle download to unload the apparatus. i.e. the External Loads

(major load) are not in application.

3. Keep pressing the Handle download and raise the Bed by rotating the Hand Wheel in

clockwise direction. Continue raising the Bed even after the initial contact between

the Test Piece and Indenter is made, till the needle on the Small Dial is aligned with

the SET mark. This indicates that an initial load of 10 kg (Pre-load / minor load) has

been applied on the Test Piece.

4. Manually rotate the Large Dial to align the ZERO Mark with the large needle.

(3)


5. Now rotate the Handle on the other direction to apply the External Loads. Keep the

External Loads in application for at least 21 seconds (dwell time).

6. After 21 seconds, unload the apparatus, as done in step 2 and record the reading on

the Large Dial. This will be the Rockwell Hardness Number for the Test Piece.

7. Lower the Bed by rotating the Hand Wheel in anti-clockwise direction and collect the

Test Piece.

OBSERVATION TABLE – 1

Sl. No. Specimen Reading (HRB) Mean Hardness (HRB)

1

Flat Mild Steel Plate

2

3


Sl. No. Specimen Reading (HRC) Mean Hardness (HRC)

1

Flat High Carbon

Steel Plate

2

3

RESULT:

1. The hardness of the mild steel test piece is found to be :

2. The hardness of the high carbon steel test piece is found to be :

Figure 1.2: Writing a particular Result after test [as per ISO 6508-1:2005(E)]

(4)


Table 1.1: Rockwell Scales and Indenters [as per ISO 6508-1:2005(E)]

Rockwell

Hardness

Scale

Hardness

Symbol Type of Indenter

Preliminary

Test Force

𝑭𝟎

Additional

Test Force

𝑭𝟏

Total Test

Force

𝑭

Field of Application

(Rockwell Hardness Test)

A HRA 1200 Diamond cone 10 kgf 50 kgf 60 kgf 20 HRA to 88 HRA

B HRB 1/16 inch Ball 10 kgf 90 kgf 100 kgf 20 HRB to 100 HRB

C HRC 1200 Diamond cone 10 kgf 140 kgf 150 kgf 20 HRC to 70 HRC

D HRD 1200 Diamond cone 10 kgf 90 kgf 100 kgf 40 HRD to 77 HRD

E HRE 1/8 inch Ball 10 kgf 90 kgf 100 kgf 70 HRE to 100 HRE

F HRF 1/16 inch Ball 10 kgf 50 kgf 60 kgf 60 HRF to 100 HRF

G HRG 1/16 inch Ball 10 kgf 140 kgf 150 kgf 30 HRG to 94 HRG

H HRH 1/8 inch Ball 10 kgf 50 kgf 60 kgf 80 HRH to 100 HRH

K HRK 1/8 inch Ball 10 kgf 140 kgf 150 kgf 40 HRK to 100 HRK

15N HR15N 1200 Diamond cone 3 kgf 12 kgf 15 kgf 70 HR15N to 94 HR15N



15T HR15T 1/16 inch Ball 3 kgf 12 kgf 15 kgf 67 HR15T to 93 HR15T



(5)


Figure 1.3: Rockwell Hardness Apparatus

Figure 1.4: The Dial Indicator showing both Rockwell B & C Scales

Figure 1.5: Different types of Indenters

(6)


REFERENCES

ISO 6508-1:2005(E) document.

Exp. No. 1 Title: To determine hardness of a flat mild steel and high carbon

steel specimen

Name of Student:

Roll No.:

Date of Experiment:

Date of Submission:

Signature of Teacher SEAL

with Date of Check

(7)


Experiment No. 2

TITLE: Brinell Hardness Test.

OBJECTIVE:

To determine hardness of a mild steel and high carbon steel specimen.

APPARATUS REQUIRED:

1. Brinell Hardness Tester [fig. 2.2 (a, b, c)]

Manufactured by Zaklady Automatyki Przemyslowej,

Poland

2. External Weights: 3000 kg for hard material, 1500 kg for

intermediate material, and 500 kg for soft material. Refer

Table 2.1 for more details.

3. Steel Ball Indenter of 10 mm diameter [fig. 2.2 (c)]

4. Brinell Microscope [fig. 2.2 (d)]

Manufactured by PZO Warszawa, Poland

THEORY:

The hardness of a material is its resistance to penetration under a localized

pressure or resistance to abrasion. Hardness test provides an accurate, rapid and

economical way of determining the resistance of material to deformation.

In this test, a Tungsten Carbide steel ball indenter of diameter D is pressed

against the surface of the test piece by a gradually applied load P, and this force is

maintained for a definite amount of time. The impression on the test piece so obtained

is measured using an optical microscope and the required Brinell Hardness Number

(BHN) or Brinell Hardness (HB) is calculated using the following relation:

𝐁𝐇𝐍 𝐨𝐫 𝐇𝐁 =𝐀𝐩𝐩𝐥𝐢𝐞𝐝 𝐭𝐞𝐬𝐭 𝐟𝐨𝐫𝐜𝐞 𝐢𝐧 𝐤𝐠𝐟

𝐀𝐫𝐞𝐚 𝐨𝐟 𝐢𝐦𝐩𝐫𝐞𝐬𝐬𝐢𝐨𝐧 𝐢𝐧 𝐦𝐦𝟐=

𝑷

𝑨

Where,

𝑃 = Applied Test Force in kgf.

𝐴 = Indented area = 𝜋 𝐷 2 𝐷 − 𝐷2 − 𝑑2 1 2

(8)


𝐷 = Diameter of steel ball indenter = 10 mm

𝑑 = Diameter of impression on the test piece

The BHN is expressed in kg/mm2. For obtaining good results, the steel ball indenter

used in this test should be well polished and free from any surface defects.

PRECAUTIONS:

The thickness of the test piece should be at least 8-10 times the depth of

indentation. Visible deformation at the back of the test piece can indicate that

the test piece is too thin.

The test should be carried out at ambient temperature within the limits of 10℃

to 35℃. However, because temperature variations may affect the results, hence

for better results, the test can be carried under controlled environment.

The test surface should be smooth and even, free from oxide scale, foreign

matters and, in particular, completely free from lubricants.

Brinell Hardness test is not recommended for materials above 650 HBW

10/3000.

PROCEDURE:

1. Place the test piece on the test piece Bed of the apparatus.

2. Raise the Bed by rotating the Hand Wheel in clockwise direction till the initial

contact between the surface of the test piece and the indenter is made.

3. Place suitable External Weights on the Yoke and close the Release Valve. The

amount of external weights attached corresponds to the test force that would be

applied on the test piece.

4. Start pumping the hydraulic fluid by moving the Handle up-and-down to

gradually increase the test force on the test piece, till the fluid overflows

through the Overflow Valve. Overflow gives an indication that the maximum

amount of test force has been applied on the test piece.

5. Keep the test force in application for about 15 seconds (dwell time).

6. Now, open the release valve to release the test force.

(9)


7. Lower the Bed and collect the test piece.

8. Measure the diameter of the impression by using the Brinell Microscope.

Hence, calculate the area of impression and the required Brinell Hardness

Number (BHN).


Sl.

No. Specimen

Diameter of

steel ball

Indenter 𝑫 𝒎𝒎

Diameter of

Impression

𝒅 𝒎𝒎

Area of

Impression

𝑨 𝒎𝒎𝟐

BHN Average

BHN

1

Flat Mild Steel

Plate

2

3


Sl.

No. Specimen

Diameter of

steel ball

Indenter 𝑫 𝒎𝒎

Diameter of

Impression

𝒅 𝒎𝒎

Area of

Impression

𝑨 𝒎𝒎𝟐

BHN Average

BHN

1

Flat High

Carbon

Steel Plate

2

3

RESULT:

1. The hardness of the mild steel test piece is found to be :

2. The hardness of the high carbon steel test piece is found to be :

(10)


Figure 2.1: Writing a particular Result after test [as per ISO 6506-1:2014(E)]

Hardness symbol HBW should be used if a Tungsten Carbide Ball Indenter is

used, where W is the chemical symbol for Tungsten. Otherwise, if a Hardened Steel

Ball indenter is used, the hardness symbol HBS should be used, where S denotes

Hardened Steel.

(11)


(a) (b)

(c) (d)

Figure 2.2: (a, b, c) Different parts of the Brinell Hardness Testing apparatus ; (d) Brinell

Microscope

(12)


Table 2.1: Test Forces for different hardness conditions and hardness range

Hardness

Symbol

Ball

Diameter

(D)

(mm)

Test force

value (F)

(kgf)

Force-diameter

index

(F/D2)

Recommended

Hardness Range

(HBW)

HBW 10/3000 10 3000 30 95.5 to 650

HBW 10/1500 10 1500 15 47.7 to 327

HBW 10/1000 10 1000 10 31.8 to 218

HBW 10/500 10 500 5 15.9 to 109

HBW 10/250 10 250 2.5 7.96 to 54.5

HBW 10/125 10 125 1.25 3.98 to 27.2

HBW 10/100 10 100 1 3.18 to 21.8

HBW 5/750 5 750 30 95.5 to 650

HBW 5/250 5 250 10 31.8 to 218

HBW 5/125 5 125 5 15.9 to 109

HBW 5/62.5 5 62 2.5 7.96 to 54.5

HBW 5/31.25 5 31.25 1.25 3.98 to 27.2

HBW 5/25 5 25 1 3.18 to 21.8

HBW 2.5/187.5 2.5 188 30 95.5 to 650

HBW 2.5/62.5 2.5 62 10 31.8 to 218

HBW 2.5/31.25 2.5 31 5 15.9 to 109

HBW 2.5/15.625 2.5 16 2.5 7.96 to 54.5

HBW 2.5/7.8125 2.5 7.8125 1.25 3.98 to 27.2

HBW 2.5/6.25 2.5 6 1 3.18 to 21.8

HBW 1/30 1 30 30 95.5 to 650

HBW 1/10 1 10 10 31.8 to 218

HBW 1/5 1 5 5 15.9 to 109

HBW 1/2.5 1 3 2.5 7.96 to 54.5

HBW 1/1.25 1 1.25 1.25 3.98 to 27.2

HBW 1/1 1 1 1 3.18 to 21.8

REFERENCES:


ASTM E10-15 and ASTM E10-01 document.

(13)


Exp. No. 2 Title: To determine hardness of a mild steel and high carbon

steel specimen.

Name of Student:

Roll No.:

Date of Experiment:

Date of Submission:


with Date of Check

(14)


Experiment No. 3

TITLE: Charpy Pendulum Impact Test.

OBJECTIVE:

To determine impact resistance of an assigned specimen in

the form of a notched bar flexure specimen.

APPARATUS REQUIRED:

Charpy Pendulum Impact test apparatus (Fig. 3.3)

V-notched bar. (Fig. 3.2)

THEORY:

A notched bar of definite geometry is broken with the single blow from a

swinging pendulum, dropped from a definite height, and the energy absorbed during the

impact is determined. This absorbed energy during the impact is the impact resistance

of the test piece.

The pendulum of mass 𝑚 𝑘𝑔 is raise to a definite height ℎ1 and then dropped

freely to swing. The striker edge of the pendulum then hits the test piece at a point just

opposite to the notch, breaks it into two pieces, and swings freely to a height ℎ2 on the

other side. Energy absorbed during the process is the energy used in breaking the

specimen, and that is equal to 𝑚𝑔 ℎ1 − ℎ2 .

PROCEDURE:

1. Place the specimen on the supports and against the anvils as shown in Fig. 3.1. The

notch should be on the side of the specimen away from the striking edge of the

pendulum and directly in line with it.

2. Raise the pendulum to a certain height ℎ1 and hold it. Record the first dial reading and

find the initial Potential Energy 𝑃𝐸 = 𝑚𝑔ℎ stored in the pendulum at this height.

The dial reading directly gives the value of 𝑚ℎ. Multiply this value with 𝑔 to get the

value of 𝑃𝐸.

3. Then release the pendulum to fall freely and rapture the specimen. The pendulum will

then rise to a maximum height ℎ2 on the other side. Record the second dial reading

and find the final 𝑃𝐸 for the pendulum at that height.

(15)


4. Now calculate the energy lost during the impact. This is the required impact resistance

of the test specimen.

OBSERVATION:

Specimen

Initial PE of

the Pendulum

at height

𝒉𝟏 = 𝑿𝟏 Joule

Final PE of

the Pendulum

at height

𝒉𝟐 = 𝑿𝟐 Joule

Energy absorbed

during impact

𝑿𝟏 − 𝑿𝟐

(Joule)

Average

(Joule)

Mild Steel Bar

RESULT:

The impact resistance of the given test specimen is found to be : ……………..… 𝑲𝑽𝟐

Here, 𝐾𝑉 is used to denote the impact resistance of the test piece. Letter 𝑽 is used for

V-notch and 𝑼 for U-notch; and the subscript 2 in 𝐾𝑉2 denotes the striker radius in

𝑚𝑚.

Figure 3.1: Placement of the test piece on apparatus supports

(16)


Figure 3.2: Geometry of the V-notched bar [as per ISO 148-1:2009(E)]

Table 3.1: Tolerances on specified test piece dimensions [as per ISO 148-1:2009(E)]

Designation Symbol

used

Nominal

Dimension

Machining

Tolerance

Length 𝑙 55 𝑚𝑚 ±0.60 𝑚𝑚

Height ℎ 10 𝑚𝑚 ±0.075 𝑚𝑚

Width

(for standard test piece) 𝑤 10 𝑚𝑚 ±0.11 𝑚𝑚

Angle of notch 𝜃 45° ±2°

Height below notch

(height of test piece minus depth of notch) 𝑥 8 𝑚𝑚 ±0.075 𝑚𝑚

Radius of curvature at base of notch 𝑅 0.25 𝑚𝑚 ±0.025 𝑚𝑚

Depth of notch 𝑧 2 𝑚𝑚 −

Distance of plane of symmetry of notch from ends of

test piece 𝑦 27.5 𝑚𝑚 ±0.42 𝑚𝑚

Angle between adjacent longitudinal faces of test

piece

𝛼 90° ±2°

(17)


Figure 3.3: Parts of the Charpy Impact Test apparatus

(18)


REFERENCE:


Exp. No. 3 Title: Charpy Pendulum Impact Test.

Name of Student:

Roll No.:

Date of Experiment:

Date of Submission:


with Date of Check

(19)


Experiment No. 4

TITLE: Compressive Stress Test.

OBJECTIVE:

To determine the compressive Strength of a given specimen.

APPARATUS:

Compressive Test apparatus

In this machine head is actuated

hydraulically and a hydraulic gauge

indicates the load. Oil is pumped from the

supply tank through control valve into the

cylinder. The piston at bottom of the

cylinder is forced upward lifting the table.

THEORY:

Compressive Stress =Compressive load

Cross − sectional Area

PROCEDURE:

1. Determine the average surface area of the specimen.

2. Place the specimen on the bottom plate at the mid position.

3. Lower the upper plate by rotating the hand wheel and fix the test specimen.

4. Select suitable speed of the load by rotating the Fluid Flow Regulator.

5. Load the machine until the specimen fails.

6. Record the compressive load from the hydraulic gauge.

(20)


OBSERVATION TABLE:

Specimen:

Sl.

No.

Length

𝒎𝒎 Breadth

𝒎𝒎

Cross-

sectional

Area

𝒎𝒎𝟐

Average Cross-

sectional Area

𝒎𝒎𝟐

Compressive

Load

𝒌𝑵

Compressive

Stress

𝒌𝑵 𝒎𝒎𝟐

1

2

3

(21)


Figure 4.1: Labeled pictures of the machines

(22)


Exp. No. 4 Title: Compressive Stress Test.

Name of Student:

Roll No.:

Date of Experiment:

Date of Submission:


with Date of Check

(23)


Experiment No. 5

TITLE: Torsion Test.

OBJECTIVE:

To determine Modulus of Rigidity 𝐶 , Breaking Torque 𝑇 and Ultimate Shear Stress

𝜏 of a mild steel specimen by conducting Torsion Test.

THEORY:

When a shaft is subjected to equal and opposite twisting

moments or torques, the shaft is said to be in torsion. To

understand this better, let us consider an axisymmetrical shaft

AB of length L with one end fixed and the other end free, as

shown in Fig. 5.1 (a). To visualize the deformation, draw

longitudinal lines and circles perpendicular to the longitudinal

lines before applying the torque. After applying the torque at

the free end, deformation will take place and the longitudinal

lines will form helixes as the circles rotate in their own planes.

This is shown in Fig. 5.1 (b).

Figure 5.1(a) Figure 5.1(b)

If the space between the circular lines is assumed to represent a circular layer of

the shaft, then the shaft can be visualized to be composed of a number of such circular

layers. When torque is applied, each circular layer will rotate against its adjacent layer,

and in this process it will impart a tangential force on its adjacent layer. Thus the

adjacent layer will develop Shear Stress to maintain its shape and size. This process

continues from the initial layer at the free end till the last layer at the fixed end and the

(24)


intensity of shear force as well as shear stress decreases as we move away from the

point of application of the torque.

Hence, due to applied torque, the material of the shaft will develop shear stress.

When the applied torque exceeds the internal stress resultants, shear strain will be

induced in the shaft. Also, the value of shear stress increases as radius increases. i.e.

shear stress is zero at the longitudinal axis, increases gradually and reaches to a

maximum value at the outer surface.

The following Torsion Equation can be derived for an axisymmetrical shaft:

𝑻

𝑱=

𝝉

𝑹=

𝑪𝜽

𝑳

Here,

𝑇 = Maximum Torque / Breaking Torque (N-m) ; [ 1 in.lbs = 0.112984825 N-m ]

=𝜋

16𝜏𝐷3 ; 𝐷 = Diameter of the shaft mm

𝑅 = Radius of the shaft (mm)

𝐽 = Polar Moment of Inertia mm4 =𝜋𝑑4

32

𝜏 = Maximum shear stress at the outer surface at a radial distance 𝑅 𝑁 𝑚𝑚2

𝐶 = Modulus of rigidity for the material of the shaft 𝑁 𝑚𝑚2

=Shear stress

Shear strain=

𝜏

𝜑

𝜃 = Angle of twist (𝑟𝑎𝑑𝑖𝑎𝑛)

𝐿 = Length of the shaft (𝑚𝑚)

PRECAUTIONS:

The test piece should be as straight as possible along the gauge length.

The grips of the test piece should not rotate while twisting the test piece.

The test should be carried out at an ambient temperature of 10℃ to 35℃ .

(25)


PROCEDURE:

1. Measure the Gauge Length of the test piece using an Inside Caliper. Also measure the

diameter along the gauge length at least at three positions and take average.

2. Rotate the handle to align the two Jaws face-to-face.

3. Insert the two Clamps at the two gripping ends of the test piece and then properly

insert the test piece in the Jaws. Keep the gripping end of the test piece having the

centering hole towards the Push Rod.

4. Fix the test piece firmly by using the Push Rod. This Push Rod is useful in

accommodating different lengths of the test piece.

5. Align the Pendulum Pointers. Also set the Pointer of the Dial Indicator to Zero.

6. Now start twisting the test piece till failure occurs. This can be done either by

switching ON the driving motor, or manually by rotating the Handle in clockwise or

anti-clockwise direction.

Figure 5.2: Test piece geometry [as per IS 1717 : 2012]

OBSERVATION:

Gauge length of the specimen, 𝐿 =

Diameter of the specimen, 𝑑 =

Breaking Torque, 𝑇 =

Angle of Twist, 𝜃 =

(26)


CALCULATION:

Polar Moment of Inertia (J)

Maximum / Ultimate Shear Stress 𝝉

Modulus of Rigidity (C)

(27)


Figure 5.2: Labeled pictures of the Torsion Test apparatus

(28)


REFERENCE:

ISO 7800 : 2003 document.

Exp. No. 5

Title: To determine Modulus of Rigidity (𝐶) , Breaking Torque

𝑇 and Ultimate Shear Stress 𝜏 of a mild steel

specimen by conducting Torsion Test.

Name of Student:

Roll No.:

Date of Experiment:

Date of Submission:


with Date of Check

(29)


Experiment No. 6

TITLE: Tension Test.

OBJECTIVE:

To determine the following parameters of

the given specimen:

1. Elongation

2. Maximum stress

3. Breaking stress

4. % age of reduction of Area

THEORY:

Refer to the following Stress – Strain diagram for ductile material.

APPARATUS:

1. Universal Testing Machine

(30)


SPECIMEN:

Draw the dimensional sketch of the specimen.

OBSERVATION:

Sl.

No.

Diameter

𝒎𝒎

Average

Diameter

𝑫 𝒎𝒎

Neck

Diameter

𝒅 𝒎𝒎

Length of

the

specimen

𝑳𝟏 𝒎𝒎

Length of

the

specimen

after

elongation

𝑳𝟐 𝒎𝒎

Maximum

Load 𝑷𝟏 𝒌𝑵

Breaking

Load

𝑷𝟐 𝒌𝑵

𝐷1 =

𝐷2 =

𝐷3 =

(31)


RESULTS:

1. Elongation = 𝐿2 − 𝐿1 =

2. Maximum stress 𝑃1 𝐷 =

3. Breaking stress = 𝑃2 𝐷 =

Therefore, % Reduction of Area = 𝜋 4 𝐷2 − 𝑑2 =

Exp. No. 6 Title: Tension Test.

Name of Student:

Roll No.:

Date of Experiment:

Date of Submission:


with Date of Check

Material Testing - Jorhat Engineering College

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